In remarks made during his official visit to southern Turkey's Adana province, Hammond said: “Russian intervention has given the regime a new full life”.

He also added that U.K. was demanding an end to targeting of civilians and siege tactics in Syria.

“Russians say they support those objectives. But, of course, what they do is something different,” Hammond added.

Russia began extensive air operations in Syria on Sept. 30 with the aim of supporting the embattled Assad regime.

While the Kremlin says its air campaign targets the Daesh militant group in Syria, some members of the western NATO alliance believe Russia is targeting groups opposed to Assad, including some that enjoy U.S. and Turkish support.

According to a report released last month by Amnesty International, hundreds of civilians in Syria have been killed by Russian airstrikes over the last three months.